Greetings Idren
I have heard of the incident when Selassie did not accept Garvey's invitation. This quite possibly did happened. It is the motivations behind it that gets sketchy. HIM may have had a pressing engagement at the time. I have never heard that it was because Selassie considered himself a multitude of races and not Black. That is an interesting idea since he met with europeans often who cleary arent black. Maybe it is this that caused Garvey's resentment and later admonishing of Haile Selassie.

I attached a link to a discussion about the situation.

Bless up